Remote control system



Oct. 3, 1950 N. B. TAYLOR 2,524,300

REMOTE CONTROL SYSTEM Filed Aug. 6, 194a Sig nal Source l3 "fixl 8 2| Other Equipment INVENTOR. Neil B. Taylor BY Patented Oct. 3 1950 REMOTE, CONTROL SYSTEM,

Neil B. Taylor, Chicago, 11., assignor to Motorola, Inc., Chicago, 111., a corporation of Illinois Application August 6, 1948, Serial No. 42,912

5 Claims.

This invention relates to remote control equip: ment and more particularly to a remotely operated lock-in switching arrangement adapted for use with communication equipment.

In communication systems there are many applications in which remote operation of various equipment is desired. It has been the usual practice to provide separate circuits for remotely controlling such switching arrangements. This, however, adds considerable expense to the system due to the requirements for leasing or otherwise providing the additional conductors necessary for the remote control operations. Carrier operated systems have been used, as for controlling radio link installations, but these systems may respond to-carriers other than the desired carrier which may be present at the control frequency. To overcome this it has been proposed to provide remote control by the use of various audio tones which may be transmitted over the same wires used for communication. In such a system, equipment is required at the remote station which is selectively responsive to the various tones and provides switching to produce the desired remote function in response to the tones. For satisfactory operation this remote equipment must provide a high degree of discrimination against noise and/or sound signals transmitted over the normal communication system. Also it is desired that the equipment he as simple and rugged as possible so that the space required and the cost of maintenance thereof is a minimum. This is particularly important when the remote unit is used in a mobile installation as space and power at such installations are quite limited.

It is, therefore, an object of the present invention to provide a simple and effective remotely operated switching system.

Another object is to provide a system which selectively responds to audio tones to provide-remote lock-in switching.

A feature of this invention is the provision of a remote lock-in switching system arranged to respond to a first pair of audio tones: to 0perate the switch, and then to resp0ndtoa second pair of tones to restore the switch.

A further feature is the provision of a remote control arrangement including a pair of electromechanical contactors responsive to individual audio tones for'actuatinga relay, and including an additional'contactor which together with one of said pair of contactors responds to audio-tones forrestoring the relay.

A still further feature of this invention is the provision of a remote control system responsive to audio tones in which a vacuum tube-Which controls a relay is rendered conducting in response to two audio tones and is held conducting by the relay, and a second vacuum tube is rendered conducting in response to one of said tones and an additional tone and is effective to block the first vacuum tube to release the relay.

Further objects, features and advantages will be apparent from a consideration of the following description when taken in connection with the accompanying drawing which illustrates a remote control system in accordance with the invention.

In practicing the invention there is provided a selective responsive switching system including three electromechanical contactors which are arranged to respond to individual audio tones. A double triode tube is included with the first section being connected in a circuit with two ofthe contactors so that when these contactors respond thefirst section will conduct and actuate a relay, the winding of which is in the output circuit of the triode section. A holding circuit is provided for maintaining a bias on the triode when the relay is actuated. The second triode section is connected in a circuit with the third contactor andone of the other contactors and arranged to conduct when these two contactors are actuated. The cathodes of the two triodes are interconnected so that when the second section conducts an increased positive bias is produced'on the cathode of the first section to block this section and release the relay. Therefore, the relay is operated when the first two tones are received and remains in operative condition until the second pair of tones are received.

Referring now more particularly to the drawing, the system includes electromechanical contactors [0, i l and !2 which may be of the type disclosed in the copending application of Marion R. Winkler, Serial No. 342, filed January 2', 1948, subject Vibrating Reed Structure. The contactors will each respondto a different frequency to intermittently close the contacts thereof when the proper frequencies are applied thereto. The windings of these electromechanical contacts are connected'in parallel to a signal source I3. It is to be pointed out that this signal source may include other signals in addition to the control signals to which the contactors i9, ll and i2 respond, as for example, voice communication signals, and may be applied to other equipment to be controlled by the selective system. The contacts of electromechanical contactors [Band I l are connectedin series with resistor I 4 and condenser I5 between plus B and ground. Contactor I is bridged by condenser I6 and resistor I! in series, and contact II is bridged by condenser l8 and resistor I9 in series. Resistor 20 is connected in parallel with condenser I5.

When a signal is applied including the frequencies to which contactors I0 and II respond, the contacts of each will be intermittently closed to provide a charge on condenser I5. That is, when contactor II] is closed a path is provided through resistor I9, condenser I8, resistor I l and condenser I which will charge both condensers I8 and I5. Then when contact II is closed condenser I8 will be shorted and resistor I'I, condenser I5, resistor I4 and condenser I5 will be connected across plus B so that condensers I6 and I5 will be charged. It is, therefore, seen that increments of charge will be applied to condenser I5 each time either of the contactors closes. This arrangement is disclosed and claimed in the copending application of Ralph J. Lense and Alfred S. I-Iolzinger, Serial No. 749,952, filed May 23, 194"], subject Selective Calling Sys tems. The resistor is effective to discharge condenser I5 but is of such value that the charge will build up rapidly on the condenser when the contactors I0 and II both operate. However, any random closing of the contactors will charge the condensers at such a slow rate that the resistor 26 will keep the condenser I5 discharged.

The voltage across condenser I5 and resistor 20 is used to control the first section of a double triode tube 26. This voltage is applied to the grid 21 of this triode to provide a bias thereon sufficient to cause the tube to conduct for a time interval which depends on the values of condenser I5 and resistor 20. A positive bias is provided for the cathode 24 of the triode by the voltage divider includin resistors M and 45 connected between plus B and ground. A relay 28 is provided having a winding 29 connected to the plate 36 of the triode 25. The relay 28 is, therefore, actuated when the triode 25 conducts to cause associated contacts 3| and 32 to change their position. The contacts 3! are effective to connect the grid 2'! of the tube through resistor 33 to plus B to provide a bias on the grid so that the tube remains conducting.

When it is desired to release the relay, tones of the frequencies to which contactors II and I2 respond are applied. The contactor I2 is bridged by condenser 35 and resistor 35. The contacts of contactors II and I2 are included in a series circuit with resistor 31 and condenser 38. The condenser 38 is bridged by resistor 39. Operation of the contactors is effective to charge the condenser 38 in the same manner as described with respect to condenser I5.

The second triode section 40 of the tube 26 includes a grid 4! connected to condenser 38. The plate 42 is connected to plus B and the cathode 43 is directly connected to cathode 24 of the first triode section. When the condenser 33 is charged to a predetermined value, the voltage thereacross will cause the triode 40 to conduct. The plate cathode circuit of the triode will therefore, draw current causing an increased current in cathode resistor 45. This will raise the potential of the cathodes to the point where the triode 25 no longer conducts because of the positive bias on cathode 24. Therefore, the relay 29 will drop out and the contacts will be restored to their normal position.

It is, therefore, seen that when the tones to which contactors l0 and I I respond are applied to the remote control system, the triode section 25 will conduct, actuating the relay 28. The holding circuit will provide a bias for keeping the triode conducting so that the switching position is mantained. Then when the tones to which contactors II and I2 respond are applied to the system the triode 40 will conduct. The output current of the triode 40 passes through resistor 45 to increase the voltage thereacross so that an increased positive potential appears on cathode 24. This is sufiicient to overcome the positive bias on the grid 21 so that the section 25 ceases to conduct and the relay is de-energized.

Resistor 2I is provided to eliminate the possibility of random voltage distribution in the circuit due to unequal capacities and random leakage resistance. Resistor 2I also provides a fixed path for the rapid discharge of condenser I6 and the condenser 35, and a path for the rapid charge of condenser I8, when the contactors are at rest. This prevents operation of the system in response to alternate application of either pair of tones. The system will therefore operate only when each pair of tones is applied together.

The selective responsive system has a high discrimination against noise as random noise will seldom include the pairs of frequencies required to trip either the lock-in or the release circuits. Also the resistors 20 and 39 across the main charging condensers will prevent the building up of a tripping voltage by random signals of the required tones. However, when tones of the proper frequencies are applied, the condensers i5 and 38 are charged very rapidly so that the system operates in a very short time.

In the system in accordance with the invention highly selective lock-in switching is provided by the use of only three contactors, a double triode tube and a single relay. This results in a very simple and compact structure which is very dependable in operation. The system is very inexpensive as compared to systems which have been previously used for this purpose.

While I have described one embodiment of my invention which is illustrative thereof it is obvious that various changes and modifications can be made therein without departing from the intended scope of the invention as defined in the appended claims.

I claim:

1. A selective responsive system including first, second and third electromechanical contactors having contacts adapted to be intermittently closed in response to signals of first, second and third frequencies respectively, first and second electron discharge valves having input and output electrodes, a relay, a first circuit including said first and second contactors, said input electrode of first electron discharge valve and said relay arranged to cause said first valve to conduct when signals of said first and second frequencies are applied to said system, said relay being connected to said output electrode of said first valve so that it is operated when said valve conducts, a second circuit including said first and third contactors and said input electrode of said second electron discharge valve arranged to cause said second valve to conduct when said first and third frequencies are applied to said system, and means interconnecting said first and second valves for blocking said first valve when said second valve conducts.

2. A selective responsive system including at least three electromechanical contactors having contacts adapted to be intermittently closed when a signal including individual frequencies to which said contactors respond is applied thereto, first and second electron discharge valves having in put and output electrodes, a relay, a first circuit including a pair of said contactors, said input electrode of said first electron discharge valve and said relay for rendering said first valve conducting in response to a signal including the fre quencies to which said pair of contactors respond is applied to said system, said relay being connected to said output electrode of said first valve so that it is operated when said valve conducts, a second circuit including a second pair of said contactors and said input electrode of said second electron discharge valve for rendering said second valve conducting in response to a signal including the frequencies to which said second pair of contactors respond is applied to said system, and means interconnecting said first and second valves for blocking said first valve when said second valve conducts.

3. A selective responsive system including first, second and third electromechanical contactors having contacts adapted to be intermittently closed in response to signals of first, sec- 0nd and third frequencies respectively, first and second condensers, first and second electron discharge valves each having an anode, a cathode and a control grid, a relay, a resistor connecting the cathodes of said first and second valves to ground, a first circuit including said first and second contactors, and said first condenser arranged to charge said first condenser when a signal including said first and second frequencies is applied to said system, said first condenser being connected to said control grid of said first valve to render said first valve conducting when said first condenser is charged, said relay being connected to the anode of said first valve so that it is operated when said valve conducts, and a second circuit including said first and third contactors and said sec-- and condenser and arranged to charge said second condenser when a signal including said first and third frequencies is applied to said system, said second condenser being connected to said control grid of said second valve to render said second valve conducting when said second condenser is charged, the current through said resistor produced by said second valve being effective to increase the bias on said cathode of said first valve to block said first valve and release said relay.

4. A lock-in remote control switching system including first, second and third frequency selective means, first and second condensers, first and second electron discharge valves each having anodes, cathodes and control grids, a relay, a resistor connecting the cathodes of said first and second valves to ground, a first circuit including said first and second frequency selective means and said first condenser for charging said first condenser when a signal including the frequencies to which said first and second frequency selective means respond is applied to said system, said first condenser being connected to said control grid of said first valve to render said first valve conducting when said first condenser is charged, said relay being connected to the anode of said first valve so that it is operated when said valve conducts, and a second circuit including said first and third frequency selective means and said second condenser for charging said second condenser when a signal including the frequencies to which said first and third frequency selective means respond is applied to said system, said second condenser being connected to said control grid of said second valve to render said second valve conducting when said second condenser is charged, the current through said resistor produced by said second valve being effective to increase the bias on said cathode of said first valve to block said first valve and release said relay.

5. A selective responsive system including first, second and third electromechanical contactors having contacts which intermittently close in response to signals of first, second and third frequencies respectively, first and second electron discharge valves each including an anode, a cathode and a control grid, a resistor connecting said cathodes of said first and second valves to ground, a relay, circuit means including said first and second contactors and said control grid of said first valve arranged to cause said first valve to conduct when a signal including said first and second frequencies is applied to said system, said relay being connected to said anode of said first valve to be operated when said first valve conducts, means including said relay for providing a bias on said control grid of said first valve so that said first valve continues to conduct, and additional circuit means including said first and third contactors and said control grid of said second valve arranged to cause said second valve to conduct when a signal including said first and third frequencies is applied to said system, said resistor providing an increased positive bias on said cathode of said first valve to block said first valve and release said relay.

' NEIL B. TAYLOR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,661,962 Robinson Mar. 6, 1928 2,165,048 Gulliksen July 4, 1939 2,173,154 Bernard Sept. 19, 1934 2,265,996 Blumlein Dec. 16, 1941 2,300,999 Williams Nov. 3, 1942 2,427,850 Gehman Sept. 23, 1947 FOREIGN PATENTS Number Country Date 261,384 Great Britain Oct. 6, 1927 

